Publication: Propuestas arquitectónicas para servidores Web distribuidos con réplicas parciales
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2005-06
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2005-09-22
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Abstract
En esta tesis se propone una arquitectura distribuida de servidor Web, basada en switch distribuido y replicación parcial de contenidos, que permite alcanzar una alta escalabilidad en cuanto a los volúmenes de datos manipulados sin que se produzca un deterioro en la fiabilidad del sistema resultante, haciendo posible además que la asignación de contenidos se adapte de forma dinámica a las necesidades del servicio. Más concretamente, las propuestas realizadas en esta tesis incluyen: Una familia novedosa de soluciones arquitectónicas de cluster Web con switch distribuido que satisface los objetivos de replicación parcial y distribución dinámica de réplicas, mitigando las debilidades relativas a la fiabilidad; un algoritmo de asignación de réplicas que hace que los elementos con mayor frecuencia de acceso sean replicados en más nodos servidores que los elementos con baja frecuencia de acceso; una estrategia de replicación dinámica de contenidos que permite determinar cuando es necesario realizar la redistribución de contenidos y cómo debe realizarse dicha redistribución; la adaptación de tres políticas de asignación de peticiones al caso de replicación parcial de contenidos: la política estática circular, la política de asignación al nodo menos cargado y la política de distribución de peticiones dependiente de la localidad de referencias (LARD). Las evaluaciones realizadas han demostrado que la fiabilidad de un sistema Web basado en cluster está limitada por la fiabilidad de su switch Web. Así mismo en esta tesis se demuestra que un sistema basado en replicación parcial que utilice un número relativamente bajo de réplicas ofrece una fiabilidad equivalente a la de un sistema totalmente replicado, aunque ofrece una capacidad de almacenamiento mucho mayor. Además, la replicación parcial no afecta negativamente al rendimiento global del sistema
In this thesis a new Web server distributed architecture is proposed. The proposed architecture is based on the usage of a distributed switch and the partial replication of contents, in such a way that a high scalability can be achieved regarding managed data volume and without a reliability loss of the resulting system. Besides, content allocation may be adapted to service needs. The proposals presented in this thesis include: a new family of architecture solutions based on a Web cluster with distributed switch which satisfies the goals of partial replication and dynamic replica distribution reducing the reliability weaknesses ; a replica allocation algorithm making the highly accessed elements to be replicated in more server nodes than the lowly accessed elements; a dynamic content replication strategy which allows to determine when content redistribution is needed and how this redistribution must be performed; the adaptation of three request dispatching policies to the case of partial content replication: round robin dispatching, less loaded node dispatching and locality aware request distribution dispatching (LARD). Evaluations have proved that the reliability of a cluster based Web system is limited by its Web switch reliability. In the same way, this thesis shows that a partial replication based system using a relatively low number of replicas offers an equivalent reliability to that of a system based on full replication, while its storage capacity is much higher. Besides, partial replication does not affect in a negative way to the global system performance
In this thesis a new Web server distributed architecture is proposed. The proposed architecture is based on the usage of a distributed switch and the partial replication of contents, in such a way that a high scalability can be achieved regarding managed data volume and without a reliability loss of the resulting system. Besides, content allocation may be adapted to service needs. The proposals presented in this thesis include: a new family of architecture solutions based on a Web cluster with distributed switch which satisfies the goals of partial replication and dynamic replica distribution reducing the reliability weaknesses ; a replica allocation algorithm making the highly accessed elements to be replicated in more server nodes than the lowly accessed elements; a dynamic content replication strategy which allows to determine when content redistribution is needed and how this redistribution must be performed; the adaptation of three request dispatching policies to the case of partial content replication: round robin dispatching, less loaded node dispatching and locality aware request distribution dispatching (LARD). Evaluations have proved that the reliability of a cluster based Web system is limited by its Web switch reliability. In the same way, this thesis shows that a partial replication based system using a relatively low number of replicas offers an equivalent reliability to that of a system based on full replication, while its storage capacity is much higher. Besides, partial replication does not affect in a negative way to the global system performance
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Arquitectura de redes, Web